Methods and apparatus for treating embolism

ABSTRACT

A method and apparatus for treating a clot in the blood vessel of a patient, and particularly the treatment of a pulmonary embolism is disclosed. The treatment includes restoring flow through the clot followed by clot removal, either partially or substantially completely. The clot treatment device is expandable into the blood vessel and may contain radial extensions that assist in restoring flow as well as in removing clot material.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/728,775 filed Nov. 20, 2012 entitled Devices and Methods forTreatment of Vascular Occlusion and U.S. Provisional Application Ser.No. 61/750,277 filed Jan. 8, 2013 entitled Devices and Methods forTreatment of Vascular Occlusion, both of which are hereby incorporatedherein by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to the apparatus and methods of endovasculartreatment of blood clots obstructing passageways in the circulatorysystem and particularly the endovascular treatment of pulmonaryembolism.

BACKGROUND OF THE INVENTION

Thromboembolism is the formation in a blood vessel of a dot (thrombus)that breaks loose (embolizes) and is carried by the blood stream toanother location in the circulatory system resulting in a clot orobstruction at that new location. For example, a clot may embolize andplug a vessel in the lungs (pulmonary embolism), the brain (stroke), thegastrointestinal tract, the kidneys, or the legs. Thromboembolism is asignificant cause of morbidity (disease) and mortality (death),especially in adults. A thromboembolism can be sudden and massive or itmay be small and multiple. A thromboembolism can be any size and athromboembolic event can happen at any time.

When a thrombus forms in the venous circulation of the body it oftenembolizes to the lungs. Such a thrombus typically embolizes from theveins of the legs, pelvis, or inferior vena cava and travels to theright heart cavities and then into the pulmonary arteries thus resultingin a pulmonary embolism.

A pulmonary embolism results in right heart failure and decreased bloodflow through the lungs with subsequent decreased oxygenation of thelungs, heart and the rest of the body. More specifically, when such athrombus enters the pulmonary arteries, obstruction and spasm of thedifferent arteries of the lung occurs which further decreases blood flowand gaseous exchange through the lung tissue resulting in pulmonaryedema. All of these factors decrease the oxygen in the blood in the leftheart. As a result, the oxygenated blood supplied by the coronaryarteries to the musculature of both the left and right heart isinsufficient for proper contractions of the muscle which furtherdecreases the entire oxygenated blood flow to the rest of the body. Thisoften leads to heart dysfunction and specifically right ventricledysfunction.

This condition is relatively common and has many causes. Some of themore common causes are prolonged inactivity such as bed rest, extendedsitting (e.g., lengthy aircraft travel), dehydration, extensive surgeryor protracted disease. Almost all of these causes are characterized bythe blood of the inferior peripheral major circulatory systemcoagulating to varying degrees and resulting in permanent drainageproblems.

There exist a number of approaches to treating thromboembolism andparticularly pulmonary embolism. Some of those approaches include theuse of anticoagulants, thrombolytics and endovascular attempts atremoval of the emboli from the pulmonary artery. The endovascularattempts often rely on catheterization of the affected vessels andapplication of chemical or mechanical agents or both to disintegrate theclot. Invasive surgical intervention in which the emboli is removed byaccessing the chest cavity, opening the embolized pulmonary arteryand/or its branches and removing the clot is also possible.

The prior approaches to treatment, however, are lacking. For example,the use of agents such as anticoagulants and/or thrombolytics to reduceor remove a pulmonary embolism typically takes a prolonged period oftime, e.g., hours and even days, before the treatment is effective.Moreover, such agents can cause hemorrhage in a patient.

And the known mechanical devices for removing an embolism are typicallyhighly complex and prone to cause undue trauma to the vessel. Moreover,such known devices are difficult and expensive to manufacture.

Lastly, the known treatment methods do not emphasize sufficiently thegoal of urgently restoring blood flow through the thrombus once thethrombus has been identified. In other words, the known methods focusprimarily and firstly on overall clot reduction and removal instead offirst focusing on relief of the acute blockage condition followed thenby the goal of clot reduction and removal. Hence, known methods are notproviding optimal patient care, particularly as such care relates totreatment of a pulmonary embolism.

OBJECTS AND SUMMARY OF THE INVENTION

In view of the foregoing it is an object of the present invention toprovide a method and system that initially restores an acceptable levelof oxygenated blood to the patient's circulatory system followed by safeand effective removal of the thrombus.

It is a further object of the present invention to treat pulmonaryembolism in a minimally invasive manner.

It is a further object of the present invention to provide a system thatdoes not cause undue trauma to the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, aspects, features and advantages of which theinvention is capable will be apparent from the following description ofembodiments of the present invention, reference being made to theaccompanying drawings, in which

FIG. 1A is a schematic view of a patient with a pulmonary embolism;

FIG. 1B is an enlarged view of the lung area of the patient depicted inFIG. 1A;

FIG. 1C is an enlarged view of the introducer device depicted being usedin the femoral vein of the patient in FIG. 1A;

FIG. 2 is a cross-sectional view of a patient's heart;

FIG. 3 is a perspective view of a patients main pulmonary artery andright and left pulmonary arteries with a clot located in the leftpulmonary artery;

FIG. 4 is a cross-sectional view of a preferred embodiment of a clottreatment device in accordance with the present invention in acompressed, undeployed state;

FIG. 5 is a top view of a preferred embodiment of a clot treatmentdevice in accordance with the present invention;

FIGS. 6A-6F are a series of cross-sectional views of a preferredembodiment of the method and device of the present invention;

FIGS. 7A-7B are a series of cross-sectional views of a preferredembodiment of the method and device of the present invention;

FIG. 8 is a cross-sectional view of another preferred embodiment of themethod and device of the present invention; and,

FIGS. 9A-9H show cross-sectional views of preferred embodiments of aclot treatment device in accordance with the present invention.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

Referring to FIGS. 1A-1C, these drawings show the typical locations in ahuman patient where pulmonary embolisms 100 occur in the pulmonaryarteries and further discloses the pathway through which access to suchpulmonary embolisms 100 is achieved. In particular, an introducer device(e.g., a hemostatic valve) 102 which supports relatively large diameterdevices is inserted into the patient into the femoral vein FV in thepelvic area of the patient. The tools and devices needed to treat thepulmonary embolism are then inserted through the introducer 102 into thefemoral vein FV through the inferior vena cava IVC to the patient'sheart.

It will be understood, however, that other access locations into thevenous circulatory system of a patient are possible and which areconsistent with the present invention. For example, the user can gainaccess through the jugular vein, the subclavian vein, the brachial veinor any other vein that connects or eventually leads to the superior venacava. Use of other vessels that are closer to right atrium RA of thepatient's heart may be attractive as this will reduce the length of theinstruments needed to reach the pulmonary embolism.

Referring to FIGS. 2 and 3, the tools/devices are then guided throughthe right atrium RA through the triscupid valve TV, into the rightventricle RV, through the pulmonary valve PV into the main pulmonaryartery (MPA). Depending on the location of the embolism 100, thetools/devices are then guided to one or more of the branches of theright pulmonary artery RPA or the left pulmonary artery LPA, includingdeeper branches thereof, to the location of the pulmonary embolism 100.

Referring to FIG. 4, an embodiment of a clot treatment device 402 forrestoring blood flow through the clot 100 and for removing at least aportion of the clot is depicted in its undeployed, or compressed state.The device 402 is constrained by a delivery catheter 606. In a preferredembodiment, the device 402 is constituted by a braided material, theends of which are captured distally by a blunt tip 405 and proximally byan attachment member 403 that connects to a pusher wire 401.

In alternative preferred embodiments, the clot treatment device 402 maybe an “over the wire” device, in which case, the pusher wire 401, theattachment member 403 and the blunt tip 405 will have a hollow centrallumen for receiving a guide wire.

In yet a further preferred embodiment, the distal end of the clottreatment device shall have a flexible, atraumatic extension from thedevice.

In preferred embodiments the clot treatment device 402 of the presentinvention has a generally cylindrical shape that, during use, provides aflow lumen for blood across a clot. The treatment device 402 is not,however, limited to a generally cylindrical shape. For example, theshape can be generally conical, generally concave or generally convexalong its axis, so long as such shapes provide the aforesaid lumen forblood flow.

In other preferred embodiments, the treatment device 402 also has aseries of radially extending portions 406 which are separated bygenerally cylindrical portions 412. It is important that the clottreatment device be porous so as to allow the flow of bloodtherethrough. In this regard, in a preferred embodiment the clottreatment device is made from a mesh or braided material. The materialcan be a superelastic material such as nitinol or an alternativematerial such as cobalt chrome alloy. The device can be made from a wirelattice, wire braid or stent. Specific preferred embodiments arediscussed throughout this specification.

Referring to FIG. 5, the deployed state of the clot treatment device 402of FIG. 4 is depicted. This preferred embodiment of the clot treatmentdevice 402 is constituted by a mesh structure that is generallycylindrical with a series of radially extending portions 406 situatedalong the axis of the device 402 and separated by a corresponding seriesof cylindrical sections 412. Optionally, the generally cylindricalsection may have individually have tapers or collectively form a conicallumen (not shown). Each of these radially extending portions 406 is inthe shape of a disk. The clot treatment device 402 is self expanding.

Referring to FIGS. 1-3 and 6A-6F, a preferred method of causing flowrestoration and clot removal/retrieval with the clot treatment device402 in a body lumen L is described.

After accessing the femoral vein and inserting a introducer device 102into the patient, a guide wire 602 is inserted into the patient andmaneuvered through the femoral vein FV into the inferior vena cava IVCto the heart. As stated above access can also be achieved through one ofthe veins leading to the superior vena cava SVC. The guide wire 602 isthen urged through the right atrium RA, through the tricuspid valve TV,through the right ventricle RV, through the pulmonary valve PV to themain pulmonary artery MPA and then to a location of the embolism/clot100 in one of the branches or lumens L of either the right or leftpulmonary artery RPA, LPA. In a preferred embodiment, the guide wire 602is extended through the clot in the body lumen L as shown in FIG. 6A

Referring to FIG. 6B, a guide catheter 604 is placed over the guide wire602 and moved to a location where a distal end of the guide catheter 604is positioned proximal to the clot 100.

At this point, the guide wire can optionally be withdrawn. However, in apreferred embodiment the guide wire 602 remains and a delivery catheter606 that is then moved through the guide catheter 604 over the guidewire 602 and is pushed through the clot 100. This is shown in FIG. 6C.

Referring to FIG. 6D, the guide wire 602 is then withdrawn and the clottreatment device 402 in its undeployed (i.e., compressed) state is thenmoved through the delivery catheter until it is disposed at the distalend of the delivery catheter 606.

The delivery catheter 606 is then retracted in a proximal directionwhile maintaining forward pressure on the clot retrieval device 402 viaits pusher wire 401 so that the clot treatment device 402 becomesexposed and released from its delivery catheter 606. The clot treatmentdevice 402 radially expands into the clot 100 and in one preferredembodiment, at least a portion of the clot treatment device 402 expandsdistal of the clot 100. As shown in FIG. 6E, at least one of theradially extending portions 406 of the clot treatment device 402 arelocated distal to the clot 100 upon expansion of the clot treatmentdevice 402.

It can be seen that upon expansion of the clot treatment device 402 asjust described, blood flowthrough the clot 100 is restored. This isdepicted with arrows 407 in FIG. 6E. More specifically, the blood is nowfree to move through the mesh of the clot treatment device 402 and exitthe clot treatment device 402 distal to the clot 100. As a result, theacute condition of blockage is corrected thus immediately improving thecirculation of oxygenated blood in the patient.

The restoration of blood flow is anticipated to equate with restorationof a substantial portion of the normal blood flow rate for the patient.In less severe. i.e., “sub massive,” pulmonary embolism patients, theclot treatment device 402 may increase blood flow rate by at least about50 ml/min, at least about 150 ml/min or between about 100 to 250 ml/min.In severe, i.e., “massive,” pulmonary embolism patients, a larger amountof the pulmonary artery flow is compromised. Hence, in some embodiments,at least about 500 ml/min of blood flow rate may be restored. Moreover,at least a portion of the flow restoration is expected to occur prior tothe removal of the clot 100, or any portion thereof.

The restoration of blood flow by the clot treatment device 402 can beachieved in a low pressure environment. For example, the pressure in thetarget vessel can be less than 60 mmHg and the blood can be venousblood, substantially non-oxygenated blood or low oxygenated blood

In addition to restoring blood flow, the expansion of the clot treatmentdevice 402 also impinges or cuts into the clot material. This enhancesthe subsequent removal of the clot 100 since portions of the clot 100collect (1) between the radially extending portions 406; (2) through thepores of the mesh forming the radially extending portions 406; (3) alongthe longitudinal cylindrical sections 412 between the radially extendingportions 406 of the removal device 402; and (4) within the clottreatment device 402 itself.

As can be understood from the above description and the drawing figures,the deployment of the clot treatment device 402 results in an outwardlyexpanding generally cylindrical force being urged against an innersurface of the clot 100. This force pushes the clot material outwardlyand creates a lumen through which blood flow is restored. As can also beappreciated, the presence of the radially extending portions 406 on theclot treatment device 402 causes the outwardly expanding generallycylindrical force to vary in magnitude along the axis of the clottreatment device 402. The force on the clot material may be greater atthe locations of the radially extending portions 406

In braided embodiments of the clot treatment device 402, deployment,i.e., expansion, of the device leads the filaments of the braid tochange their angular orientation with respect to the axis of the device.This angular change may improve or enhances adherence of clot materialto the clot treatment device 402.

After the clot treatment device 402 has been expanded and blood flowrestored, the user then retracts the clot treatment device 402 in aproximal direction as shown in FIG. 6F. In one embodiment, the clottreatment device 402 and the delivery catheter 606 are pulled backsimultaneously into the guide catheter 604. This is followed by theentire apparatus (i.e., clot treatment device 402, delivery catheter 606and guide catheter 604) being withdrawn through the heart and the venouscirculation and out from the body.

As further shown in FIG. 6F, the clot treatment device 402 may becomeelongated as it is being withdrawn into the guide catheter 604 due tothe resistance it encounters from the presence of clot material of theclot 100. The presence of the radially extending portions 406 may allowelongation that enhances the capability of the device 402 to capture themaximum amount of clot material. This is further discussed below withrespect to the surface area and expansion ratio of preferred embodimentsof the clot treatment device 402.

It will be appreciated that variations in the above-described method arecontemplated. For example, in certain circumstances a guide catheter 604may not be necessary or desirable and the user may chose to use only thedelivery catheter 606 for placing and manipulation of the clot treatmentdevice 402. As a further example, the clot may be of such a nature thatthe user may desire repeat the above-described process, or at leastportions of it, in order to more fully remove the clot 100 or clotmaterial.

Referring next to FIGS. 7A-7B, it may be advantageous to include the useof a collection or funnel catheter 612 to assist in the removal of theclot 100. Such a funnel catheter 612 has an expandable portion 614 atits distal end and may be situated between the guide catheter 604 andthe delivery catheter 608 or may be part of the guide catheter 604. Inthe presence of the collection catheter 612, the clot treatment device402 is pulled proximally into the collection catheter 612 such that theclot or portions of it are captured within the collection catheter 612.In an alternative embodiment, the collection catheter 612 can be pusheddistally over the clot treatment device 402 and capture the clot, orportions thereof, in that manner. If the collection catheter 612 isseparate from the guide catheter 606, the collection catheter with theclot treatment device 402 is then pulled into the guide catheter forultimate removal of all devices (and the clot) from the patient.

In certain circumstances, it may be advisable to remove the clot 100without capturing it in the guide catheter 606 or the collectioncatheter 612 (if used) and remove the clot 100 by withdrawing the entiresystem, e.g., guide catheter 605, delivery catheter 604, clot treatmentdevice 402 and collection catheter 612 (if used) simultaneously.

In a preferred embodiment the collection catheter 612 is constructed asa mesh or braid or stent structure. Such structure assists in retrievingand containing the clot material in the withdrawal process. In yetfurther preferred embodiments, the collection catheter 612 containsstructural features to assist in the expansion of the funnel portion 614and to hold the funnel portion 614 open towards the wall of the bloodvessel. Such features (not shown) include interwoven support struts,self expanding material (e.g., nitinol), longitudinal wire supports,stent supports, polymeric webbing, etc.

In another embodiment of the present invention, a vacuum apparatus maybe used to aid in the removal of the clot material. Referring to FIG. 8,a syringe 802 is shown connected to a vacuum manifold 806 that is influid communication with the proximal end of the guide catheter 604. Atthe time the clot treatment device 402 (and clot material) is beingwithdrawn into the guide catheter 604 (or the collection catheter 612),vacuum is applied by pulling on the syringe. Alternative sources ofvacuum 804 are also acceptable, e.g., a vacuum pump. A system is alsocontemplated whereby vacuum is actuated automatically when the clottreatment device 402 (and the clot material) is being withdrawn. Arepresentation of the effect of the use of vacuum can be seen withreference to FIG. 7B which shows how vacuum causes flow 701 into thecatheter 612.

Referring now to FIGS. 9A-9H, alternative preferred embodiments of theclot treatment device 402 are disclosed.

Referring to FIG. 9A, the radially extending portions 406 between thegenerally cylindrical sections 412 of the clot treatment device 402 aredefined by a cylindrical disk shape with a rounded triangularcross-section.

Referring to FIG. 9B, the radially extending portions 406 between thegenerally cylindrical sections 412 of the clot treatment device 402 aredefined by a cylindrical disk shape with a rounded triangularcross-section wherein the diameter of the disk increases along thelength of the device 402 thus forming a conical exterior extent.

Referring to FIG. 9C, the radially extending portions 406 between thegenerally cylindrical sections 412 of the clot treatment device 402 aredefined by a cylindrical disk shape with a rectangular cross-section.

Referring to FIG. 9D, the radially extending portions 406 between thegenerally cylindrical sections 412 of the clot treatment device 402 aredefined by a cylindrical disk shape with a linear (non-rounded)triangular cross-section.

Referring to FIG. 9E, some of the radially extending portions 406between the generally cylindrical sections 412 of the clot treatmentdevice 402 are defined by a cylindrical disk shape with a roundedcross-section and others have a rectangular cross section.

Referring to FIG. 9F, the radially extending portions 406 between thegenerally cylindrical sections 412 of the clot treatment device 402alternate between cylindrical disk shape with a T-shaped cross-sectionand a flare-shaped cross-section.

Referring to FIG. 9G, the radially extending portions 406 between thegenerally cylindrical sections 412 of the clot treatment device 402 aredefined by a partial cylindrical disk shapes.

Referring to FIG. 9H, the radially extending portions 406 between thegenerally cylindrical sections 412 of the clot treatment device 402 aredefined by tabs and bumps or protuberances arising from the cylindricalsurface of the device 402.

In this regard, it is noted that the radially extending portions 406provide greater surface area along the device than a device that isuniformly cylindrical. Such increased surface area facilitates thetreatment and/or retrieval of a much larger portion of the clot 100 thanis generally feasible with a uniformly cylindrical device. For example,in a preferred embodiment of the clot treatment device 402, the devicewill have an external surface area between 1.5× and 6× the surface areaof a uniformly cylindrical device of the same general diameter of thecylindrical sections 412. In other preferred embodiments the ration willbe 2× to 4×.

This is advantageous particularly during retraction of the clottreatment device 402 through the clot 100. As shown in FIG. 6F, the clottreatment device 402 may become elongated as it is being withdrawnthrough the clot 100. Such elongation causes the clot material toencounter greater surface area of the clot treatment device 402 thanwould otherwise occur with a device that was only generally cylindrical,i.e., that did not incorporate radially extending portions 406.Accordingly the clot treatment device 402 is particularly adept atcapturing the maximum amount of clot material during withdrawal.

The clot treatment device 402 is intended for use in large vessels,i.e., vessels with a diameter greater than 8 mm. For example, thediameter of the pulmonary arteries typically range from 15 to 30 mmwhereas the first branches of the pulmonary arteries typically rangefrom 10 to 15 mm and the secondary and tertiary branches typically rangefrom 5 to 10 mm. At the same time, however, it is important to minimizethe size of catheter providing access to the clot 100. Accordingly, theclot treatment device 402 has a large expansion ratio. In a preferredembodiment the expansion ratio from the diameter of the cylindricalsections 412 in the collapsed state to the expanded state will bebetween 4 and 8. In another preferred embodiment the ratio will bebetween 5 and 7. The large expansion ratio also enables the formation ofa flow channel in the clot 100 that is large, e.g., on the order of 4-8mm.

The radially extending portions 406, in their fully expanded positionare intended to have a size that matches the diameter of the targetblood vessel. However, the diameters may be slightly larger than thevessel diameter so to apply greater radial force against the bloodvessel (without causing trauma) in those circumstances when it isdesirable to improve clot collection. Similarly, in those circumstanceswhere there is a concern of creating trauma on delicate blood vessels,the radially extending portions 406 may have a diameter that is smallerthan the vessel diameter. It is contemplated that different sizes of thedevice 402 will be available for selection by the user for a particularpresentation of the patient.

As for the length of the clot treatment device 402, it is known that atypical pulmonary embolism will have a length within the range betweenabout 2 cm and 10 cm and sometimes between about 1 cm and 20 cm.Accordingly, in a preferred embodiment, the clot treatment device 402will have a length that exceeds the length of the embolism so that aportion of the clot treatment device is positioned distal of the clot100 during expansion.

With regard to the delivery catheter 606, in a preferred embodiment foruse with a pulmonary embolism, the size will be around 1 F-6 F. Smallerdiameters will pass through the clot 100 more easily. In addition, thedelivery catheter 606 may have stiffness characteristics to assist inmaking sure the delivery catheter 606 passes through the clot in asmooth manner. Such stiffness characteristics include self expandingnitinol wire braids or stent structures that are contained within thestructure of the delivery catheter 606. The delivery catheter 606 alsohas sufficient flexibility so that it may carry the clot treatmentdevice 402 and still pass through a tortuous vessel path as describedabove starting with insertion of the delivery catheter 606 in thefemoral vein FV.

In some preferred embodiments, the method and device in accordance withthe present invention may reduce the Mean Resting Pulmonary ArteryPressure (MRPAP). Upon at least partial relief from the clot 100, MRPAPmay be reduced by about 20-50 mmHg to a normal range of 8-20 mmHg. Insome embodiments, the reduction in MRPAP may be about 25-50%. In someembodiments, the reduction in MRPAP may be about 15% to 40% and in otherembodiments between about 30% and 75%.

Such a reduction in MRPAP can occur in two steps. The first step is whenthe clot treatment device 402 is first deployed and blood flow is atleast partially restored. The second step is when the clot treatmentdevice 402 is retracted and at least some of the clot 100 is removedfrom the vessel.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

What is claimed is:
 1. A method of treating a pulmonary embolismcomprising: delivering an embolectomy device through the heart to apulmonary embolism that at least partially restricts blood flow througha pulmonary vessel, wherein the embolectomy device comprises anexpandable cylindrical section and at least first and second radialexpansion members configured to expand outwardly from the cylindricalsection, wherein the cylindrical section is between the first and secondradial expansion members; deploying the embolectomy device within thepulmonary embolism so as to restore blood flow through said pulmonaryembolism, wherein deploying the embolectomy device comprises expandingthe cylindrical section within the pulmonary embolism such that thecylindrical section forms an expanded flow channel through the pulmonaryembolism and expanding the radial expansion member to a greater extentthan the cylindrical section, and wherein at full expansion of thecylindrical member the radial expansion member projects outward from thecylindrical member, and wherein the cylindrical section has a firstlength in a longitudinal direction and each of the first and secondradial expansion members have a length in the longitudinal directionthat is less than the first length of the cylindrical section at fullexpansion; moving the embolectomy device and at least a portion of thepulmonary embolism along the pulmonary vessel; and withdrawing theembolectomy device and at least a portion of the pulmonary embolism fromthe pulmonary vessel.
 2. A method according to claim 1, whereindeploying the embolectomy device comprises expanding a plurality ofradial extensions of said embolectomy device.
 3. A method according toclaim 2, wherein at least one of said plurality of radial extensions isexpanded distal to said pulmonary embolism.
 4. A method according toclaim 1, wherein said deploying the embolectomy device comprisesexpanding a plurality of cylindrical portions and a plurality of radialexpansion members of said device, and wherein the cylindrical portionsare between the radial expansion members.
 5. A method according to claim4, wherein the embolectomy device comprises a continuous mesh and thecylindrical portions and the radial expansion members are integrallyformed of the mesh, and expanding the plurality of radial expansionmembers and the cylindrical portions comprises expanding the mesh to agreater extent at the radial expansion members than at the cylindricalportions.
 6. A method according to claim 4, wherein deploying theembolectomy device comprises expanding said device such that a surfacearea of said embolectomy device expands within a range of at least twotimes to four times the surface area of a uniformly cylindrical device.7. A method according to claim 1, wherein deploying the embolectomydevice comprises causing filaments of said embolectomy device to changeangle with respect to an axis of said device and thereby increaseadherence of material of said pulmonary embolism to said embolectomydevice.
 8. A method according to claim 1, further comprising applyingvacuum during said retracting of said embolectomy device.
 9. A methodaccording to claim 1, wherein the cylindrical section and the radialexpansion member are self-expanding.
 10. A method of treating apulmonary embolism comprising: accessing a venous vessel of a patient;inserting a catheter into said venous vessel and urging the catheterthrough said venous vessel, through chambers of the patient's heart andinto a pulmonary artery until a distal end of the catheter is located ata distal end region of a pulmonary embolism of the patient; delivering aclot treatment device having a flow portion and at least first andsecond radial expansion members through the catheter and into thepulmonary embolism, wherein the flow portion is between the first andsecond radial expansion members; expanding the flow portion from acompressed state to an expanded elongated state such that a diameter ofthe flow portion increases by a ratio of at least 4:1 to 8:1 and therebyforms a flow channel that restores blood flow through the pulmonaryembolism; expanding the radial expansion member to a greater extent thanthe diameter of the flow portion in the expanded elongated state, andwherein at full expansion of the flow portion the radial expansionmember projects outward from the flow portion, and wherein the flowportion has a first length in a longitudinal direction and each of thefirst and second radial expansion members have a length in thelongitudinal direction that is less than the first length of the flowportion at full expansion; retracting the clot treatment device and atleast a portion of the clot material along the vessel.
 11. A methodaccording to claim 10, wherein the device includes a plurality of radialexpansion members and the method comprises expanding the plurality ofradial expansion members to a greater extent than the flow portion. 12.A method according to claim 11, wherein at least one of said pluralityof radial extensions is expanded distal to said pulmonary embolism. 13.A method according to claim 11, wherein expanding the flow portion andthe radial expansion member comprises causing filaments of said clottreatment device to change angle with respect to an axis of said deviceand thereby increase adherence of material of said pulmonary embolism tosaid clot treatment device.
 14. A method according to claim 11, furthercomprising applying vacuum during said retracting of said expanded clottreatment device.
 15. A method according to claim 11, wherein the flowportion and the radial expansion member are self-expanding.
 16. A methodaccording to claim 11, wherein said expanding of said embolectomy devicecomprises expanding said device such that a surface area of said clottreatment device expands within a range of at least two times to fourtimes the surface area of a uniformly cylindrical device.
 17. A methodaccording to claim 11, wherein said expanding includes expanding aportion of said clot treatment device distal to said pulmonary embolism.18. A method according to claim 17, wherein said expanding includesexpanding said clot treatment device so that it exceeds the length ofsaid pulmonary embolism.
 19. A method according to claim 11, whereinsaid restoring of said blood flow reduces a mean resting pulmonaryartery pressure within a range of about 20-50 mHg.
 20. A method oftreating a pulmonary embolism comprising: accessing a venous vessel of apatient; inserting a delivery catheter containing a clot treatmentdevice into the venous vessel, through the venous circulatory system ofthe patient, and through the heart to a clot of a pulmonary embolism;urging the delivery catheter through the clot; deploying the clottreatment device from the delivery catheter and causing an outwardlyexpanding radial force along a cylinder to be urged against an innersurface of said clot to form a channel of not less than about 4 mm to 8mm entirely through said clot and causing at least first and secondradial expansion members to expand to a greater extent than the channel,wherein the cylinder is between the first and second radial expansionmembers, and wherein at full expansion the cylinder has a first lengthin a longitudinal direction, the first and second radial expansionmembers project outward from the cylinder, and each the first and secondradial expansion members have a length in the longitudinal directionthat is less than the first length of the cylinder; and withdrawing saidclot treatment device through said clot and thereby removing clotmaterial from said clot.
 21. A method according to claim 20, whereinsaid outwardly expanding radial force comprises generating a force thatvaries in magnitude along a length of said clot treatment device.
 22. Amethod according to claim 21, wherein said variation in magnitude is aresult of a plurality of radial expansion members expanding along anaxis of the clot retrieval device.
 23. A method according to claim 20,wherein said causing said outwardly expanding radial force is comprisedof expanding the cylinder of the clot treatment device in said clot. 24.A method according to claim 21, wherein said generating of a force thatvaries in magnitude comprises expanding radial expansion members thereonin said clot.
 25. A method according to claim 20, wherein withdrawingsaid clot treatment device includes elongating said clot treatmentdevice as said clot treatment device contacts material of said clot. 26.A method according to claim 20, wherein said deploying of said clottreatment device includes cutting into material of said clot.
 27. Amethod according to claim 20, wherein said deploying of said clottreatment device includes causing filaments of said clot treatmentdevice to change angle with respect to an axis of said device andthereby increase adherence of material of said clot to said clottreatment device.
 28. A method according to claim 20, wherein thecylinder and the radial expansion member are self-expanding.
 29. Amethod according to claim 20, further comprising applying vacuum duringsaid withdrawing of said clot treatment device.
 30. A method accordingto claim 20, wherein said deploying of said clot treatment deviceincludes increasing blood flow rate through said clot by at least about50 ml/min.